MR T1 and T2 relaxations in cysts and abscesses measured by 1.5 T MRI.

OBJECTIVES

The main objective of this study was to make a comparison between the relaxation rates in jaw cysts and abscesses. Such a comparison should provide quantitative information for MR image analysis.

METHODS

A phantom containing 20 odontogenic jaw cysts and 11 jaw abscesses was imaged with 1.5 T MR. T(1) measurements were performed by using a mixed sequence of inversion recovery and spin echo, while T(2) measurements were carried out by the Carr-Purcell Meiboom-Gill (CPMG) sequence. Cystic fluids and abscesses were compared statistically.

RESULTS

In cysts and abscesses, respectively, the mean 1/T(1) was 0.9355 s(-1) and 0.8245 s(-1) and the mean 1/T(2) was 2.4575 s(-1) and 4.7073 s(-1). The 1/T(2) in cysts was very highly significantly different from that in abscesses (p = 0.0001). Both T(1) and T(2) were linearly proportional to material contents. T(2) relaxivities [26.458 ml (g s)(-1) for abscesses and 21.455 ml (g s)(-1) for cysts] were higher than T(1) relaxivities [5.4766 ml (g s)(-1) for abscesses and 10.075 ml (g s)(-1) for cysts].

DISCUSSION

Present T(2) measurements differentiate cysts from abscesses with a confidence interval of 95%. Because in vivo and in vitro image contrasts are changed by the same parameters, the T(2) findings should present valuable information for in vivo MRI. Hence the significant difference and the relaxivities may provide quantitative information for clinicians and researchers making image analyses.

CONCLUSION

T(2) may differentiate cysts from abscesses. The difference in T(2) is related to the material content of samples.